The present invention relates to an optical low-pass filter to prevent an image degradation by filtering a wave of an optical false signal, and a prism optical system equipped with a prism to perform color separation to a plurality of color bands.
In recent years, in a case in which image pickup devices such as a CCD and a CMOS are used in a video camera and a digital still camera, it is necessary to hold, in a barrel, an optical low-pass filter for filtering unwanted high-frequency components, so as to prevent generation of colors false signals and moiré fringes and so on.
An optical low-pass filter of a related art for a video camera with a color separation prism is provided with a board having a phase elimination characteristic described below in patent documents 1 and 2.    [patent document 1] Japanese Patent Application Publication H11-218612    [patent document 2] Japanese Patent Application 2001-272632